Hi Alex, did you ever find an answer to this? Looking to do the same thing

I'd like to also send attestation data back in packed (or other format) to prove the passkey was created in my app, etc In order to offer device bound passkeys

Hi, I'm curious if you managed to solve this and how you are doing the check in Android. Also, how are you ensuring the passkey is device bound - looking at similar behaviour

Did you ever solve this error?